Naphthalides and phthalides

ABSTRACT

THIS INVENTION RELATES TO PHENOL PHTHALEIN INDICATOR DYES CONTAINING AS THE RING-CLOSING MOIETY, A NAPHTHALIDE GROUP OR A CARBOXYPHTHALIDE GROUP POSSESSING A CARBOXY SUBSTITUENT IN EITHER THE 4- AND/OR 7-POSITION OF THE PHTHALIDE RING. IN A PREFERRED EMBODIMENT, THE PHENOL RADICALS ARE SUBSTITUTED WITH A HYDROGEN-BONDING GROUP ON A CARBON ATOM ADJACENT TO THE CARBON ATOM CONTAINING THE PHENOLIC -OH. THESE DYES, DUE TO THE NAPHTHALIDE OR CARBOXYPHTHALIDE RING-CLOSING MOIETY EXHIBIT IMPROVED STABILITY IN HIGHLY ALKALINE MEDIA AND WHEN SUBSTITUTED WITH HYDROGEN-BONDING GROUPS AS IN THE THE PREFERRED EMBODIMENT, POSSESS A RELATIVELY HIGH PKA AS WELL.

States Patent NAPHTHALID S AND PHTHALIDES lt'ljyron S. Simon, West Newton, and David P. Waller, Arlington, Mass., assignors to Polaroid Corporation,

Cambridge, Mass. 1 '-'-No Drawing.JFiled Jan. 4, 1971, Ser. No. 103,864 a, l :Int.Cl.C07d 7/26 U.S.i'Cl. 260-4432 R 18 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND; OF THE INVENTION (1) Field of the Invention The present invention relates to novel chemical compounds, and more specifically, it relates to a new class of phenol phthalein indicator dyes. In a particular aspect it relates to phenol phthaleins useful as optical filter agents in photographic processes for protecting an exposed photosensitive material from post-exposure fogging during development in the presence of extraneous incident light.

(2) Description of the Prior Art A number of photographic processes by which images may be developed and viewed within seconds or minutes after exposure havebeen proposed. Such processess geneifally jeinployfaprocessing composition which is suitably dist'ribute'd,betweentwo. sheet-like elements, the desired image being carried by one of said sheet-like elements. The, resulting images may be in black-and-white, e.g., in silver; or'in one or more colors. Processing may be conducted in or outside of a camera. The most useful of such processes are the diffusion transfer processes which have been proposed for forming silver or dye images, and several of these processes have been commercialized. Such processes have in common the feature that the final image is a function of the formation of an image-wise distribution of an image-providing reagent and the diifusion transfer of said distribution to or from the stratum carrying the final image, whether positive or negative.

;U-.S.' Pat. 6,415,644 discloses a composite photosensitive structure, particularly adapted for use in reflection type photographic diffusion transfer color processes. This structure comprises a plurality of essential layers including, in sequence, a dimensionally stable opaque layer; one or more silverhalide emulsion layers having associated therewith dye image-providing material which is radiation and processed by interposing, intermediate the silver halide emulsion layer and the reception layer, an alkaline processing composition providing the first pH and containing a light-reflecting agent, for example, titanium dioxide to provide a white background. The light reflecting agent (referred to in said patent as an opacifying agent) also performs an opacifying function, i.e., it is effective to mask the developed silver halide emulsions and also acts to protect the photoexposed emulsions from postexposure fogging by light passing through the transparent layer if the photoexposed film unit is removed from the camera before image formation is complete.

In a preferred embodiment, the composite photosensitive structure includes a rupturable container, retaining the alkaline processing composition having the first pH and light-reflecting agent, fixedly positioned extending transverse a leading edge of the composite structure in order to efiFect, upon application of compressive pressure to the container, discharge of the processing composition intermediate the opposed surfaces of the reception layer and the next adjacent silver halide emulsion.

The liquid processing composition distributed interme-' diate the reception layer and the silver halide emulsion, permeates the silver halide emulsion layers of the composite photosensitive structure to initiate development of the latent images contained therein resultant from photoexposure. As a consequence of the development of the latent images, dye image-providing material associated with each of the respective silver halide emulsion layers is individually immobilized as a function of the point-topoint degree of the respective silver halide emulsion layer photoexposure, resulting in imagewise distributions of mobile dye image-providing materials adapted to transfer, by diffusion, to the reception layer to provide the desired transfer dye image. Subsequent to substantial dye image formation in the reception layer, a sufiicient portion of the ions of the alkaline processing composition transfers, by diffusion, to the polymeric neutralizing layer to effect reduction in the alkalinity of the composite film unit to the second pH at which dye image-providing material is substantially nondiffusible, and further dye image-provid-v ing material transfer is thereby substantially obviated.

The transfer dye image is viewed, as a reflection image, through the dimensionally stable transparent layer against the background provided by the reflecting agent, distributed as a component of the processing composition, intermediate the reception layer and next adjacent silver halide emulsion layer. The thus-formed stratum effectively masks residual dye image-providing material retained in association with the developed silver halide emulsion layer subsequent to processing.

In the copending U.S. Patent Application Ser. No. 786,352 of Edwin H. Land, filed Dec. 23, 1968, nowabam cloned, and U.S. Patent Application Ser. No. 101,968, filed Dec. 28, 1970, now U.S. Pat. No. 3,647,437, in part a continuation of Ser. No. 786,352, an organic light-absorbing reagent (or optical filter agent), such as a dye, which is present as a light-absorbing species at the first pH and which may be converted to' a substantially nonlight-absorbing species at the second pH is used in conjunction with the light-refiecting agent to protect the selectively exposed silver halide emulsions from post-exposure fogging when development of the photoexposed emulsions is conducted in the presence of extraneous incident actinic radiation impinging on the transparentlayer of the film unit.

In copending U.S. Patent Application Ser. No. 103,392 of Myron S. Simon and David P. Waller, filed Jan. 4, 1971, now U.S. Pat. No. 3,702,245, pH-sensitive dyes derived from certain hydroxy-substituted carbocyclic aryl compounds, viz., particular phenols and naphthols are disclosed as useful as optical filter agents for absorbing incident radiation actinic to selectively exposed photosensitive materials within a predetermined wavelength range in the longer wavelength region of the visible spectrum. Certain of the novel dyes disclosed therein, namely indicators which contain a carboxy-phthalide or naphthalide as the ring-closing moiety bonded to two p-hydroxyphenyl radicals each substituted with a hydrogen-bonding group are among the indicator dyes comprising the subject matter of the present invention. Such dyes find particular utility as optical filter agents in photographic processes employing highly alkaline processing solutions.

SUMMARY OF THE INVENTION It is the primary object of the present invention to provide novel phthalein indicator dyes derived from phenols.

It is another object of the present invention to provide phenol phthalein indicator dyes which exhibit improved stability in alkaline media.

It is a further object of the present invention to provide phenol phthalein indicator dyes useful as optical filter agents in photographic processes for preventing postexposure fogging of a selectively exposed photosensitive material during development in the presence of incident light.

Other objects of this invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the processes involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

According to the present invention, phenol indicator dyes are provided which contain as the ring-closing moiety, a naphthalide or a carboxy phthalide possessing at least one carboxy group in the 4- and/ or 7-position including dyes wherein the phenol radicals are substituted with hydrogen-bonding groups, which dyes will be defined with greater particularity hereinafter.

The indicator dyes of the present invention, like phthalein indicators in general such as phenol phthalein and phenol naphthalein, possess spectral absorption characteristics which are reversibly alterable in response to changes in environmental pH. These dyes possess a highly colored form capable of absorbing visible radiation in alkaline media at a first pH value above their respective pKa and a substantially colorless form, i.e., a form which is substantially non-light-absorbing in the visible spectrum in less alkaline media at a second pH value below their respective pKa. By pKa is meant the pH at which about 50% of the dye is present in its light-absorbing form and about 50% is present in its non-light-absorbing form.

It will be appreciated that such compounds will find utility in titrations and other analytical procedures where phthalein indicator dyes are commonly employed, for example, to measure changes in pH value as reflected by the change in color of the dye from one color to another or from colored to colorless or vice versa. The indicator dyes of the present invention, however, compared to the phthaleins in general use possess one or more properties in addition to their color-changing characteristics which render them useful as optical filter agents in photographic processes performed under alkaline conditions, such as those described above.

' For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS that phenol indicator dyes which contain a napthalide ring-closing moiety exhibit good stability 'in aqueous alkali in comparison to phenol indicator dyes which contain a simple, i.e., unsubstituted phthalide group as the ring-closing moiety. The latter indicators tend to be unstable in alkali and in strongly alkaline media tend to lose color quite rapidly. It has now' been discoveredv that these phthalide indicatordyes mayberenderedstable in alkaline media like the naphthalides bysubstituting a carboxy group in the 4- and/ or 7-position of the phthalide ring. According to the present invention, it has also been discovered that the pKa of phenol phthalidesnndhaphthalides in general, i.e., the pKa that generates color, may be raised by substituting hydrogen;bonding.gr ppps on the phenol radicals ortho to the phenolic hydroxy groups.

The indicator dyes of the present invention maybe represented by the formula:

wherein A and B are selected from two I radicals and two radicals wherein R is a hydrogen-bonding group having a negative charge in basic solution and X representsthe' atoms necessary to complete a' ring-closing" moiety selected from a naphthalideand a phthalide substituted. with a carboxy group in at least one of the 4- and 7-posijtions, said A and B radicals being when X represents a naphthalideaThesrespectivenaphe thalide and carboxyphthalide ring-closing moieties are illustrated below: 7

wherein at least one of R andR isaicarboxykgroup In the above formula, any hydrogenabon'ding group may be used that is capable of raisingthe:pKa. The ass'o-q ciation of two atoms through hydrogen to form a hydro;

gen bond between orwithin moleculesis well%known.'

115 When hydrogen is attached to a electronegative atom. for example, or N, the resultant bond is polarized. If directed toward another atom (M) with an'unshared pair ofelectrons, the hydrogen acts as a bridge between the atoms (OH M) due to the electrostatic attraction to both atoms between which the hydrogen proton can be transferred. In the present invention an intramolecular hydrogen bond is formed between the p-hydroxy group and an adjacent hydrogen-bonding group, i.e., a group containing a heteroatom possessing an active unshared.

pair of electrons, such as, O, N, S or halogen, e.g., R, which has arfree electron pair or a negative charge in basic solution and which is capable of forming a 6- or 7-membered and preferably a 5- or 6-membered hydrogen-bonded ring with the p-hydroxy group. Preferably, the heteroatom in the hydrogen-bonding group has attached to it a proton which is more acidic than the proton on the phenolic OH and ionizes in basic solution to a negative charge. Such groups include, for example, carboxy; hydroxy; o-hydroxyphenyl; bis trifiuo'romethyl carbinol; sulfonamido NHSO R wherein R may be alkyl, aryl, alkaryl); and sulfamoyl (SO -NHR' wherein R may be alkyl, aryl, alkaryl) Suitable R and R' substitutents include branched or straight chain alkyl, e.g., methyl, ethyl, isopropyl, n-butyl, t-butyl, hexyl, octyl, dodecyl, hexadecyl, octadecyl and eicosanyl; aryl, e.g., phenyl and naphthyl; and alkaryl, e.g., benzyl, phenethyl, phenylhexyl, p-octylphenyl and p-dodecylphenyl.

Where it is desired that the indicator dye be substantially immobile or non-diffusible in the processing solution, compounds containing a sulfamoyl or sulfonamido substituent afford the distinct advantage of allowing the immobilizing function to be combined with the hydrogen bonding function by selecting sulfonamido or sulfamoyl (SO NHR') groups containing as R or R an immoblizing group, such as, hexadecyl or pdodecylphenyl.

The compounds represented in the above formula may contain substitutents other than those specified. Besides the hydrogen-bonding groups, the A and/or B radicals may contain additional substituents and likewise, the ringclosing moiety may contain other substituents as may be desired.

In the preferred embodiment of the present invention,

both the carboxy-phthalides and naphthalides are substituted with hydrogen-bonding groups as represented in the following formula:

(II) R HO OH wherein R and X have the same meaning as in Formula (I) above.

By substituting the indicator dyes with hydrogen-bonding groups as defined above, a substantial increase in pKa may be achieved. This property together with their good stability in alkali render them especially useful as optical filter agents in photographic processing. Moreover, where methyl, ethyl, isopropyl, t-butyl, octyl, hexadecyl, and eicosanyl; aryl, such as, phenyl and naphthyl; alkaryl, such as, benzyl, phenethyl, phenylhexyl, and p-dodecylphenyl; alkoxy, such as, methoxy, ethoxy, butoxy, l-ethoxy-2-(fl-ethoxyethoxy) and octadecyloxy; aryloxy, such as phenoxy, benzyloxy and naphthoxy; alkoxyalkyl, such as methoxyethyl, ethoxyethoxyethyl and dodecyloxyethyl; halo, such as, fiuoro, bromo and chloro; sulfo; carboxy; hydroxy; and amino including monoand disubstituted amino, e.g., N-alkylamino and N,N-dialkylamino. Such substituents may be substituted on the first and/or second phenol radical and/or ring-closing moiety.

Specific examples of phenol indicator dyes within the scope of the present invention are as follows:

so -mt-c n C O OH Various methods may be employed in preparing the indicator dyes described above. Phthalein dyes including naphthalides and carboxy-phthalides may be prepared by reacting the appropriate anhydride or acid chloride, e.g., naphthalic or hemimellitic anhydride with the selected phenol at elevated temperatures usually in the presence of a suitable catalyst, such as a Lewis acid catalyst.

Another method of preparing these phthaleins comprises reacting the selected phenol with naphthalaldehydic or carboxyphthalaldehydic acid in the presence of a mild acid catalyst, e.g. toluene-p-sulfonic acid, to yield the corresponding (na)phthalidyl-substituted intermediate which is oxidized by treating with dichlorodicyanoquinone or other suitable oxidizing agent. The oxidized intermediate is then reacted with another mole of the selected starting phenol in the presence of an acid catalyst to yield the desired dye. This method of preparing phenol phthaleins and phthaleins derived from other selected aromatic compounds forms the subject matter of copending US. Patent Application Ser. No. 108,662

of Alan L. Baerror, filed Jan. 21, 1971.

The following Examples are given to further illustrate the present invention and are not intended to limit the scope thereof.

EXAMPLE 1 Preparation of the compound of formula (1) Hemimellitic anhydride (7.68 gms., 0.04 mole) and crushed zinc chloride (4.73 gms., 0.04 mole) were added with stirring to phenol (9.41 gms., 0.1 mole) in a 100- ml. 3-nec-k flask in an oil bath. The mixture Was heated to 150 C. under nitrogen with stirring. The dark ma-.

genta solution formed was allowed to stir for 20 hours.

The solution then was cooled to 90 C. and ml. of

50 water was added. The excess phenol was removed by steam distillation leaving an oil-white precipitate. The

precipitate was dissolved in 100 ml. of 5% aqueous sodium hydroxide and filtered. The alkaline solution was acidified with 10% hydrochloric acid until the magenta color disappeared. The white precipitate formed was collected by filtration and dried and then recrystallized to give 9.6 gms. (67% by weight yield) of the titled compound as white crystals (melting point 246 C.).

EXAMPLE 2 Preparation of the compound of formula (2) The compound prepared in Example 1 above (5.0 gms., 0.015 mole) was dissolved in 100 ml. of acetic acid in a 3-neck flask equipped with a nitrogen inlet and magnetic stirrer which was chilled in an ice bath. The solution was cooled to 18-20 C. To the stirred solution was added dropwise 1.9 gms. (0.031 mole) of nitric acid in 3 ml. of acetic acid over a 10 minute period. The yellow solution was allowed to warm to 70 26 C. and was stirred for two hours. The reaction mixture was then poured into 150 ml. of ice with stirring. A yellow precipitate formed which was filtered and dried and recrystallized from ethyl acetate-hexane to give 5.45

, gms. (81% by weight yield) of the title compound (melting point 250 C.).

1 1 EXAMPLE 3 Preparation of the compound of formula (13) The compound prepared in Example 2 above (2.26 gms., 0.005 mole) was dissolved in 25 ml. of ethanol and 100 ml. of dichloromethane in a Parr bottle. To this solution was added 0.5 gm. of a palladium on carbon, and the compound was shaken for 17 hours. After the theoretical amount of hydrogen was consumed, p-dodecylbenzyl-sulfonyl chloride (3.88 gms., 0.010 mole) in 50 ml. of acetone and then 3.95 gms. of pyridine was added to the Parr bottle under a flow of nitrogen. The reaction mixture was then shaken at room temperature for 14 hours. The resulting brownish solution was filtered to remove the catalyst, and 200 ml. of ethyl acetate was added to the filtrate. The ethyl acetate solution was washed with 5% hydrochloric acid; dried with magnesium sulfate; filtered and evaporated to a brown gum which was taken up in dichloromethane and placed on a dichloromethane-silica gel column. Elution with dichloromethane-3% acetone gave the title compound which was recovered 'as white crystals (1.15 gms., 22% by weight yield.)

EXAMPLE 4 Preparation of the compound of formula (4) Using the procedure of Example 1 above, freshly distilled o-cresol (51.8 gms., 0.48 mole) was reacted with hemimellitic anhydride (38.4 gms., 0.20 mole) in the presence of crushed zinc chloride (27.3 gms., 0.20 mole) to yield 43.6 gms. of the title compound (melting point 280 C. dec.).

EXAMPLE 5 Preparation of the compound of formula (6) Using the procedure of Example 2 above, the compound prepared in Example 4 (24.3 gms., 0.062 mole) dissolved in 350 ml. of acetic acid was reacted with 70% nitric acid (12.6 gms., 0.140 mole) to yield 26.4 gms. of the title compound (melting point 277 C.).

EXAMPLE 6 Preparation of the compound of formula (14) The compound prepared in Example 5 (1.68 gms., 0.0035 mole) was dissolved in 25 ml. of the ethyl acetate and 25 ml. of dichloromethane in a Parr bottle. To this was added 5% palladium on carbon, and the solution was shaken for 16 hours with 40 lbs. of hydrogen. After the theoretical amount of hydrogen Was consumed, p-dodecylbenzenesulfonyl chloride (2.50 gms., 0.0072 mole) in 37 ml. of acetone was added to the Parr bottle followed by 2 ml. of pyridine. The reaction mixture was then shaken at 26 C. under nitrogen for 12 hours. Following the reaction by TLC (20% methanol-dichloromethane on silica gel), the intermediate amine indicator formed by hydrogenation disappeared and the sulfonamide product was formed. The brownish reaction solution was then filtered and 200 ml. of ethyl acetate was added. The solution was washed with 5% hydrochloric acid; dried with magnesium sulfate; filtered and evaporated.

The resulting brownish-orange gum was taken up in dichloromethane and put on a dichloromethane-silica gel column. Elution with dichloromethane and with 3% acetone-dichloromethane removed several bands of impurities. Increasing to 5% acetone-dichloromethane removed the product. The solution containing the product was evaporated to give a yellow glass which was taken up in just enough dichloromethane to dissolve. The product was precipitated with hexane, filtered, and dried to give the title compound, an off-white solid (1.138 gms., melting range 9496 C.).

' EXAMPLE 7 Preparation of the compound of formula (11) A mixture of 3.85 gms. (0.025 mole) of 2,5-dime 12 thoxyphenol and 2.11 gms. (0.01 mole) of hemimellitic anhydride acid chloride were heated until-tliemixture became homogeneous. Thereafter, the mixturet'was cooled to room temperature and 1.36 gms. (0.01 'mole) of zinc chloride added and the resulting mixture heated at approximately 90 C. for l /2 .hOl1rs.

After adding ice and 10% hydrochloric acid (25 cc.), the excess phenol was reniovedfrom the reaction mixture by steam distillationijTheEremaining solid was dissolved in 10% aqueoussodium, hydroxide and filtered. The alkaline solution was acidified with 10% hydrochloric acid in the cold, and the precipitate formed was filtered and washed with water. After drying air,-the precip-' itate was taken up in chloroform and put bn acliloroform-silica gel column. Elutionflwith a 50-50 mixture of chloroform and methanol [gave 63 mg. of compoun which was recrystallized fromchloroform. EXAMPLE 8 Preparation of the compound ofjform "a (27) Aluminum trichloride (4.0 gms.) was added to a solution of biphenol (6.0 gms.) intetrachloroethane (15 ml.) with stirring. The solution was-brought to reflux and 3,3- dichloronaphthalide (2.5 gins. )"in tetrachloroethane (10 ml.) was added dropwise over-about an hour. The red solution was stirred at reflux overnightand poured hot onto ice/water. A yellowish gum separated which was steam distilled. The cdoled mixture ofgum rny solid-water was partitioned between water-chloroform. The water was discarded and the chloroform layer was washed with water until neutral, dried dowii' to an oil and taken up in 10% aqueous sodium hydroxide,('75 ml.). The bluepurple solution Was filtered an'd acidified. The gummy solid formed was taken up in chloroform, washed, dried and taken down to a brown oil. The oil was placed on a Florisil-chloroform colunm. Elution with chloroform removed a few impurities. Further elution with 5% methanol-chloroform removed the product-which was collected and again chromatographed on a logr isil column eluted with chloroform. All of the fractions collected, were combined, dried and the resulting brown oil was dissolved in about m1. of dichloroethane. The white solid that precipitated upon" standing was reinoved by filtration and dried to yield the title compound (melting range 225 -226 C.).

EXAMPLE: 9 a

Preparation of the compound of formula (26) I The title compound was prepared by reacting biphenol and hemimellitic anhydride according to the procedure given in Example 1 above.

EXAMPLE 10- Preparation of the compound of formula (25) EXAMPLEtl Preparation of'the compoiiiid of formula (9) if desired, or the 7-carb.oxyphthalide may be isolated from .the initial precipitate from the reaction mixture by recrystallization as detailed in Example 1.

Because of the-naphthalide or carboxyphthalide ringclosing moiety, the indicator dyes of the present invention as represented inlFormulae (I) and (II) above exhibit good stability in alkaline media. The enhanced stability in alkali has been demonstrated by determining color retention of the dyes in strong aqueous alkali. In the procedure used, the respective dyes were dissolved in 2M aqueous sodium hydroxide andthe color of each solution measured spectrophotometrically immediately upon mixing and again after ten minutes to determine if any decolorization occurred upon standing.

In one comparison using this procedure, it was found that phenol phthalein d'e c'o'lorized almost instantaneously in the strongly alkaline solution with less than 1% of the color being retained after 10 minutes whereas phenol 7- carboxyphthalein (Example 1 above) and phenol naphthalein both showed 100% color retention after minutes. (The phenol naphthalein used was prepared in a conventional manner by reacting phenol and 3,3-dichloronaphthalide in the presence of stannic chloride. This compound also may be prepared according to the procedure disclosed by G. F.*Jaubert, Berichte, 28, 991-994 (1895) by reacting naphthalic anhydride and phenol in the presence of aluminum chloride.) Also, it was found that a mixture of two isomers, namely, phenol 4-carboxyphthalein and phenol 7 carboxyphthalein showed 100% color retention after 10 minutes indicating the stability of the 4-carboxy compound.

Inanother comparison, it was 'found that biphenol phthalein like phenolphthalein decolorized very rapidly in strong alkali with less than 1% color retained after 10 minutes. Biphenol carboxyphthalein (Example 9 above) and biphenol naphthalein,(-Example8 above) both showed color retention of 100% after -=10 minutes. (The biphenol phthalein employed was prepared by reacting biphenol and hemimellitic anhydride; according to the procedure given in Example 1 above.)

In a further comparison, it was" found that o-cresol phthalein in 2M aqueous sodium hydroxide after 10 min utes retained only 3% of its initial color whereas o-cresol carboxyphthalein (Example 4 above) retained 100% of its initial color.

As noted previously,'the" indicator dyes of the preferred embodiment as represented in Formula (H) possess a relatively high pKa of about 11 or more in addition to good alkaline stability. For example, phenol, 7-carboxyphthalein (formula 1) and phenol" 4-carboxyphthalein (formulal20) both have a pKa of about 9.6. In comparison, "pyrocatecol' 7 carboxyphthalein (formula 9); o-dodecylbenzylsulfonamidophenol 7-carboxyphthalein (formula 13); o-dodecylbenzylsulfonamidocresol 7 carboxyphthalein (formula 14); and biphenol 7-carboxyphthalein (formula 26) have a pKa of 11.2; 12.8; 12.9; and 13.4, respectively. From a further comparison of pKa measurements, it was found that biphenol naphthalein (formula 27) has a pKa as compared to a pKa of 9.7 for phenol naphthalein.

Since most commercially useful photographic processes are conducted under alkaline conditions, any of the indicatopdyes of the present invention due to their alkaline stability are suitable for use as optical filter agents in photographic processes where development of a photosensitive material is conducted in the presence of extra neofis incident ligl tr 'The dyes described above havea highly colored, light absorbing form in alkaline media at a pH above their respective pKa and'a substantially colorless form, i.e., a form whichis'substantially non-light-absorbing in the visible region in less alkaline media at a pH below their respective pKa. For use in such processes, an indicator dye or dyes ni'aybe selected'from the aforementioned class of compounds which will be in a colored or light-absorbing form at the particular pH employed during development and which may be converted to a substantially non-light-absorbing form subsequent to at least the initial stages of development to permit viewing of the final image. In photographic processes where the optical filter agent is retained in association with the final image formed, it may be readily converted to a form which does not interfere with viewing of the image and which does not detract from the brilliance, hues and other properties of the image.

In its preferred embodiment, the present invention pro-' vides indicator dyes that are particularly useful in diffusion transfer processes and especially in diffusion transfer photographic processes employing composite photosensitive elements such as those described in aforementioned US. Pat. 3,415,644. In such processes, a highly alkaline processing composition having a pH of 13-14 or higher is employed so that it is desirable to use an optical filter agent having a pKa of 11 or preferably 12 or higher that will provide protection from incident actinic radiation during the processing interval but subsequent to the initial stages of the development may be rapidly converted to its colorless form to permit early viewing of the final image.

When utilized in diffusion transfer processes employing composite photosensitive elements, the indicator dyes used as the optical filter agents may be initially disposed in a layer of the composite film unit but preferably are initially disposed in the processing composition applied subsequent to selective photoexposure of the photosensitive structure. When incorporated into the processing composition, it is desirable that the dyes selected exhibit good stability in highly alkaline media in addition to efiicient absorption in the visible spectrum and a high pKa. Also, the, dyes employed as optical filter agents are preferably substantially non-dilfusible in the alkaline processing composition in order to achieve optimum efiiciency as a radiation filter and to prevent diffusion of filter agent into layers of the film unit where its presence may be undesirable.

Indicator dyes which possess these preferred characteristics are those represented in Formula (H). These indicator dyes possess the desired unique combination of properties, namely, (1) efiicient absorption of actinic radiation within the wavelength range of about 500 nm. to 700 nm., (2) a high pKa of 11 or more, (3) stability in highly alkaline media, and optionally, (4) non-diifusibility in aqueous alkali. As noted above, the photographic use of these dyes as optical filter agents in photographic processes is disclosed and claimed in copending US. Pat. Application Ser. No. 103,392 filed concurrently herewith.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A compound of the formula:

wherein A and B are the-same and are selected from two radicals and two on a R radicals wherein R is a hydrogen-bonding group selected from hydroxy, carboxy, o-hydroxyphenyl, sulfonamido and sulfamoyl; -R' is selected from hydrogen, methoxy and alkyl having 1 to 3 carbon atoms; R" is selected from hydrogen, methoxy, N and NH R" is selected from hydrogen, methoxy and alkyl having 1 to 3 carbon atoms; and X represents the atoms necessary to complete a ring-closing moiety selected from naphthalide and phthalide substituted with at least one carboxy group in at least one of the 4- and 7-positions, said A and B radicals being when X represents naphthalide.

2. A compound as defined in claim 1 wherein X represents phthalide substituted with at least one carboxyl group in at least one of the 4- and 7-p0sitions.

3. A compound as defined in claim 2 wherein X represents 7-carboxyphthalide.

4. A compound as defined in claim 2 wherein A and B are 5. A compound as defined in claim 2 wherein A and B are 6. A compound as defined in claim 5 wherein R is sulfonamido.

7. A compound as defined in claim 5 wherein R is ohydroxyphenyl.

8. A compound as defined in claim 2 wherein X represents 4-carboxyphthalidei v 9. A compound as defined in claim 1 wherein X represents naphthalide and A and B are I 10. A compound as definedin claim 9 wherein R is ohydroxyphenyl.

11. A compound as defined in claim 5 wherein R is hydroxy,

' 1'6 12. The compound of the formula: I 3 3 m a:

17 A compound of the formula:

wherein A and B are the same and are selected from two 10 radicals and two 011 I ORII III radicals wherein R is a group containing a heteroatom possessing an active unshared pair of electrons selected from O, N and S, said heteroatom possessing a proton more acidic than the proton of the adjacent OH and ionizing to a negative charge in basic solution to form an intramolecular hydrogen bond with said -0H, said group forming a 5-, 6- or 7-membered hydrogen-bonded ring with said OH; R is selected from hydrogen, methoxy and alkyl having 1 to 3 carbon atoms; R" is selected from when X represents naphthalide.

18. A compound as defined in claim 17 wherein A and B are References Cited UNITED STATES PATENTS 4/1950 Green 260-343.3X 4/1961 Korbl 260--343.3X

0 JOHN M. FORD, Primary Examiner U.S. Cl. X.R. 

